1. Field of the Invention
This invention concerns a door closer of the kind (herein called "of the kind specified") including a tension member acted on by spring means under the control of a uni-directionally operative fluid damping means which serves to regulate the rate of movement of a door, with which the closer is installed, in the direction of closure without restricting significantly the rate of movement in the direction of opening.
2. Description of the Prior Art
Door closers are known in a wide variety of forms specially adapted for various purposes. One such type (for example as shown in U.S. Pat. No. 4,115,897) includes a body for fitting to the face of a door and an articulated arm which is secured to the door frame. Whilst this type can readily be made adjustable because the housing is at all times accessible, it is not entirely acceptable for use in domestic premises for aesthetic reasons.
Another type (for example as shown in British Pat. specification No. 978,967) which includes a rotatable spindle through which movement is transmitted to the door can be concealed in the door frame, but is not entirely suitable for domestic use because of difficulties in installation, and moreover is generally not suitable for installation to an existing door.
For domestic, and many other uses, door closers of the kind specified are generally preferred, that is to say those which operate essentially by linear movement of a tension member, and more especially the type including a housing which in use is mounted within the thickness of the door itself (for example as described in French patent specification No. 1,587,528) and it is this type of door closer to which the invention relates.
It is recognised that where the rate of closure of a door is restricted by a damper of some kind, it is desirable to be able to relieve the operation of the damper, or render it ineffective, just before the door reaches its closed position so that the resistance afforded by any latch or catch on the door will be overcome to ensure that the door closes fully and is latched. This may be achieved, in the case of an hydraulic damper, by means of a suitable fluid by-pass. Because such closers act at the hinged edge of the door a very small movement of the closer corresponds to a large movement of the free edge of the door, and typically a factor of thirty times or more may be involved.
Thus, if the fluid by-pass is to operate correctly, the closer must be installed very accurately. In practice this is difficult to achieve and requires much skill. Firstly, the precise depth to which the housing is inserted in the door from the hinged edge thereof is difficult to control. Secondly, the width of the gap between the hinged edge of the door and the door frame when the door is closed may vary appreciably in different installations.
For these reasons, the amount of unrestricted travel at the free edge of the door while the damper is rendered inoperative may vary between zero and its design maximum purely according to the manner in which the closer is installed.